Process for the production of carbonyl compounds



nitrohydrocarbon salts. Among these may Patented Dec. 23, 1941 UNITEDSTATES PATENT OFFICE BOCESS FOB m PRODUCTION OI CABBONYLCOIPOUNDSKenneth Johnson. 'ierre Hante, Ind., aasignor to Purdue ResearchFoundation, Lafayette, Ind, a corporation of Indiana No Drawing.Application March 28, 1940, Serial No. 326,053

8 Claims. (Cl. 260-493) My invention relates to a process for theproduction of carbonyl compounds, and more specifically to an improvedprocess for the production of aldehydes and ketones from aliphaticnitrohydrocarbons.

It has been observed that aldehydes and ketones can be produced fromnitroparaflins by subjecting alkali salts of the nitroparafiins to theaction of acids. Yields up to 70% of the theoretical yield have beenobtained by this process, (J. U. Nef, Ann. 288, 263). Although thisreaction has been known since Nefs work in 1894, yields in excess of 70%have not been obtained up to the present time.

I have now discovered that improved yields of aldehydes and ketones canbe obtained by effecting the reaction under conditions which preventlocal alkalinity in the reaction mixture. The very pronounced effect ofalkalinity in the reaction mixture may be seen from the fact that ifacid is introduced into a solution of an alkali metal salt of anitrohydrocarbon, practical- 1y no carbonyl compounds are formed;whereas, if the nitrohydrocarbon salt is slowly introduced into an acidsolution, carbonyl compounds are produced. Even in this latter. case,however, the yields may be seriously reduced by localized alkalinity inthe reaction mixture.

I have found that the occurrence of local alkalinity in the reactionmixture may be inhibited to a large degree by employing a relativelyhigh acid concentration, preferably utilizing a considerable excess oftotal acid over that required for the reaction, and by introducing thenitrohydrocarbon salt very slowly into the acid solution whilethoroughly agitating the latter.

I have also found that local'alkalinity in the reaction mixture may beminimized by employing nltroh'ydrocarbon salts of relatively weak basesrather than the alkali metal salts which have previously been employed.The alkaline earth metal salts of the nitrohydrocarbons, for example,are less basic than the alkali metal salts, and on/ introduction into anacid solution are less likely to create zones of local alkalinity.

An additional advantage of the use of the alkaline earth metal salts ofthe nitrohydrocarbons is the fact that if sulfuric acid is employed asthe converting agent, the resulting alkaline earth metal sulfate isinsoluble, and the unused mentioned the salts of the nitroparamns. suchas nitroethane, l-nitropropane, 2-nitrobutane. nitrohendecane, and thelike, and of the nitrocycloparaflins. such as nitrocyclohexane. Myprocess is particularly adapted for the production ofaldehydes andketones from the salts of the lower nitroparafnns, and especially thosecontaining from 2 to 4 carbon atoms.

The alkaline earth metal salts of the nitrohydrocarbons may be preparedin accordance with known procedures, as, for example, by ing thenitrohydrocarbon with an aqueous suspension of an' alkaline earth metalhydroxide. The resulting aqueous suspension of the nitroparaflln saltmay then be added directly to the acid solution, or the salt may beseparated and added in anhydrous form. Alternatively. the salt may bedissolved in a suitable organic solvent, but in such case the solventshould be completely miscible with the acid solution in order to preventlocalized alkalinity in the reaction mixture,

Any acid may be employed as the converting agent in my process, if it issufficiently soluble in the reaction medium to produce a concentrationsuiiiciently high to prevent localized alkalinit in the reactionmixture. Preferably, an acid should be employed which dissociates to agreater extent than the base from which the nitrohydrocarbon salt wasformed. The strong mineral acids are very satisfactory in this respect,when employed with alkaline earth metal salts, and in view of theirlow'cost it is unnecessary, from a practical standpoint, to attempt theuse of organic acids. The concentration of the acid employed may varyover a relatively wide range, e. g., from 5%-95% by weight in the caseof sulfuric acid. I prefer, however, to employ an acid concentrationequivalent to at least 20% sulfuric acid by weight. Sufficient totalacid should be present in the solution to constitute at least oneequivalent per sulfuric acid may then be recycled, making possible acontinuous process.

My process is adapted for carbonyl compounds from any of the aliphaiggthe production of mole of the nitrohydrocarbon salt to be introducedinto this solution, and in general I prefer to employ a considerableexcess over this minimum. If a relatively weak acid is employed with anitrohydrocarbon salt of a relatively strong base. a very large excessof acid should be used, and the reaction mixture should be verythoroughly. agitated during the addition of the salt. In the case of acontinuous process, of course, the rate of addition of acid to thereaction zone should be so proportioned to the rate of addition of thenitrohydrocarbon salt as 55 to provide the desired excess of acid.

2 aaoasvs ture. Operating outside of these limits would involveunnecessary expense, and is not therefore desirable from a practicalstandpoint. It is to be understood, however, that these are not to betaken as limiting temperatures for the operation of my process.

In ca rying out my pro ess in a single batch operation. an' aqueousslurry of an alkaline earth metal salt of a nitrohydrocarbon maysuitably be slowly added to a well agitated solution of sulfuric acid.Since the reaction is exothermic. nitrous oxide is evolved, and some ofthe carbonyl compound produced may be carried 01! with the nitrousoxide. To prevent this. the acid solution may be maintained at a lowtemperature, e. g., 0., or the reaction vessel may suitably be equippedwith a reflux condenser. After all of the nitrohydrocarbon salt has beenadded, the

resulting mixture may be filtered to remove the. alkaline earth metalsulfate, and the carbonyl compound may then be recovered by knownmethods, for example, by distillatio The above process may be adaptedfor continuous operation by continuously introducing into the reactionvessel an excess of sulfuric acid simultaneously with the introductionof the nitrohydrocarbon salt, continuously removing theresultingm'ixture from the vessel, filtering, distilling andcontinuously recycling the distillation residue as a part of thesulfuric acid introduced into the reaction vessel. Such a continuousprocess could, of course. be modified in numerous I obvious ways, as,for example, by distillinig prior to filtration, or by maintaining thereaction mixture at a sufficiently high temperature to distill thealdehydes or ketones directly from the reaction vessel. Any suchmodifications are, of

course, to be considered as within the scope of my invention.

My invention may be further illustrated by the following specificexamples:

' Example I Approximately parts by weight of I-nitrobutane was dissolvedin approximately parts by weight of a sodium hydroxide solutioncontaining 8 parts by weight of sodium hydroxide. The resulting solutionof the sodium salt of l-nitrobutane was introduced into a sulfuric acidsolution comprising approximately 18 parts byweight of concentratedsulfuric acid (sp. 1.84) and 50 parts byweight of water. Thebutyraldehyde resulting from this reaction was recovered by distillationand determined by titra-' Approximately 15 parts by weight orl-nitrobutane was dissolved in approximately.100 parts by weight of asodium hydroxide solution containing a parts by weight of sodiumhydroxide. The

resulting salt solution was slowly added to a welle agitated sulfuricacid solution comprising 46 parts by weight of concentrated sulfuricacid, and parts by weight of water. The yield of butyraldehyde was 79%or the theoretical yield.

Example III Approximately 15 parts by weight of l-nitrobutane wasintroduced into a suspension of 6 parts by weight of calcium oxide and100 parts by weight of water, and the resulting mixture was agitated fora sufiicient time to promote the formation of the calcium salt ofl-nitrobutane. The resulting suspension was slowly dropped into asulfuric acid solution comprising 46 parts by weight of concentratedsulfuric acid and parts by weight of water, which was maintained atapproximately 6 C. The yield of butyraldehyde was 84% of the theoreticalyield.

Example IV The procedure of Example III was employed,

utilizing l-nitropropane in place of l-nitrobutane. The yield ofpropionaldehyde was 79.5% of the theoretical yield.

Example V The procedure of Example III was employed, utilizingnitroethane in place of l-nitrobutane. The conversion of nitroethane toacetaldehyde was approximately 77%. The presence of unreactednitroethane indicated a yield substantially higher than 77 Example VIExample VII Approximately 17 parts by weight'of 2-nitrobutane wasintroduced into a suspension of apisproxlmately 7 parts by weight ofcalcium hydroxide and .75" parts by weight of water. The resultingsuspension of the calcium salt of 2-nitrobutane was slowly introducedinto a sulfuric acid solution comprising 46 parts by weight ofconcentrated sulfuric acid and 150 parts by weight of water. The yieldof methyl ethyl ketone was 85.5% of the theoretical yield.

Example VIII I Example IX Approximately 150 parts by weight ofnitrocyclohexane was introduced into a sodium hydroxide solutioncomprising 60 parts by weight of. sodium hydroxide and 400 parts byweight of water. This mixture was heated to effect reaction, and afterall of the nitrocyclohexane had dissolved, the resulting salt solutionwas cooled bonyl .compound tainlng an excess of acid over and slowlyintroduced into an agitated solution or suliuric acid comprisingapproximately 370 parts by weight of concentrated sulfuric acid, and 500parts by weight of water, which was maintained at approximately C. Theyield of cyclohexanone was approximately 11.5% of the theoretical yield.

It is to be understood, 0! course, that the above examples are merelyillustrative, and do not limit the scope of my invention. As haspreviously been pointed out, other nitrohydrocarbon salts may betransformed into their corresponding carbonyl compounds, and acids otherthan sulfuric acid may be employed for this urpose. Other expedients forpreventing substantial local alkalinity in the reaction mixture may alsobe'used. In general it may be said that the use of any equivalents orany modifications of procedure, which would naturally occur to thoseskilled, in the art, is included within the scope of my invention.

My invention now having been described, what I claim is: Y 1

1. A process for the production of a carbonyl compound comprisingintroducing a nitro-hydroparamn salt sufliciently low, and the rate ofagitation suiiiciently high to prevent substantial local alkalinity inthe reaction mixture.

4. In a process for the production of a carbonyl compound from anitrohydrocarbon, the step which comprises introducing. an alkalineearth metal salt of a nitrohydrocarbon into an acid solution.

5. In a process for the production of a carbonyl compoundirom anitroparaiiin, the steps which comprise introducing an alkaline earthmetal salt of a, nitroparafiininto a solution of a strong mineral acidand maintaining the rate of introduction of said nitroparaflin saltsulfficiently low, and the acid concentration and rate of agitationsufllciently high, to prevent substantial local alkalinity in thereaction mixture.

6. In a process for the production of a carbonyl compound from anitroparaiiin, the step which comprises introducing an alkaline earthmetal salt of a nitroparaffin into an acid. solution of a concentrationat least equivalent to v 20% sulfuric acid.

carbon salt into an acid solution, the acid being sufllciently solublein the reaction medium to produce 2, In a process for bonyl compound bythe introduction or a nitrohydrocarbon salt'into an acid solution,theimprovement which comprises maintaining the rate oi introduction ofnitrohydrocarbon salt sufan. acid concentration suliiciently-hig'h toprevent localized alkalinity in the reaction mixture where the reactionis occurring.

the production or a car-' ficiently low, .and the acid concentration andrate or agitation sufllciently high to prevent substantial localalkalinity in the reaction mixture.

'3. In a process for the production oi -a carirom a nitroparafiin, thesteps which comprise paraiiininto an acid I at least equivalent to 20%sulfuric acid, conthat required to react with said nitroplramn salt, andmaintaining the rate of introductionor said introducing a salt or anitro-. solution of a concentration steps -bonyl compound and alkalinefate, and recycling-the residual sulfuric acid "'1. In a process for theproduction or a carbonyl compound selected irom the group consisting oialdehydes and ketones from a nitroparai'iln containing from 2 to 4carbon atoms, the which. comprise introducing the calcium salt of. saidnitroparaflin into a sulfuric acid solution or at least 20%concentration by weight containing an excess or acid over that requiredto react with said nitroparaflln salt, and maintaining the. rate ofintroduction of said salt sufficiently low, and the rate of agitationsufliciently high to prevent substantial local alkalinity in thereaction mixture.

8. A continuous process for the production of a carbonyl compoundirom anitrohydrocarbon, which comprises introducing an alkaline earth metalsalt of said nitrohydrocarbon into a sulfuric acid solutlo separatingthe resulting carearth metal sulsolution.

'. KENNETH JOHNSON.

